1. Field of the Invention
The present invention relates to radio paging receivers utilized in the paging of information containing a mixture of alphanumeric characters and characters, such as Chinese or Japanese characters, which require a larger number of bits for their representation (hereinafter referred to simply as "Chinese or Japanese characters").
2. Description of the Related Art
In recent years, advances in the functionality of radio paging receivers have included a move from receiving messages that comprise numerals only to receiving messages comprising alphanumeric characters and, in some regions, Chinese or Japanese characters. The representation of such characters requires the use of a larger number of bits, with the result that the number of bits needed to represent one character has increased. Moreover, because character-based messages have become possible, message size itself has increased.
At present, characters represented using a larger number of bits, such as Chinese or Japanese characters, are dealt with by using a segmentation scheme for alphanumeric characters in a special way. Namely, data sequences segmented by an alphanumeric segmentation scheme are combined in groups of two and assigned to a Chinese or Japanese character code table. It is also possible to have a mixture of alphanumeric characters and Chinese or Japanese characters in the same message.
The use of such a mixture of characters will be explained, taking as an example a system which represents Chinese or Japanese characters using 16 bits and alphanumeric characters using 8 bits. In the example system, the most significant bit of a Chinese or Japanese character code is a "1", while the most significant bit of an alphanumeric code is a "0", and the system makes use of this difference. The segmentation of the received data is based on 8 bits. The most significant bit of a data sequence segmented from the received data is ascertained. If this is a "0", the following data is also segmented on an 8 bit basis and its most significant bit ascertained. If this most significant bit is a "1", the processor considers the two groups of 8 bits as a combined group of 16 bits. Whether data represent an alphanumeric character or a Chinese or Japanese character can be ascertained by such a method, which therefore makes it possible to mix the two types of characters.
However, although a conventional radio paging receiver can receive a mixture of alphanumeric characters and Chinese or Japanese characters in the manner described above, various problems have been encountered with this method. Namely, it is affected by how the Chinese or Japanese characters are assigned to the Chinese or Japanese character code table. If the size of the code table is such that the Chinese or Japanese character codes use all 16 bits, or if the code table includes areas where the most significant bit is a "0", it will be impossible to represent those Chinese or Japanese characters of which the most significant bit is a "0", and it will be necessary either to move such data to another location, or to delete it. These code tables are standardized for use in a given region and cannot be altered simply for the sake of radio paging receivers. Nevertheless, hitherto there have been character codes which cannot be used unless amendments were made to the code table of the relevant region.
Meanwhile, a problem encountered in recent years has been that the trend towards sending larger messages has meant that the air time occupied by one message has increased. This has come about as follows. Namely, the increasing use of characters in messages and the increasing number of bits required per character has meant that although numerals, for example, can be represented using very few bits (4 bits), they have to be sent in a form that is matched to the number of bits needed to send a character, which means that a large number of wasted bits are sent. A large amount of the data in a message is in this unnecessary portion, and to this extent there is a wasteful use of air time.
The present invention overcomes problems of the sort described above. It is an object of this invention to provide a radio paging receiver capable of processing data which has been segmented by a plurality of previously specified segmentation schemes as a message which occupies little air time. This object is achieved by attaching, at the transmitting side, data segmentation information (information which indicates the number of bits into which subsequent data is to be segmented), changing over the message data segmentation scheme (the number of bits into which the data is segmented) in the course of the message, and making the radio paging receiver capable of recognizing the segmentation information.